1. Field of the Invention
The present invention relates generally to a Spatial Modulation (SM) method, and transmitting and receiving apparatuses using the same in a Multiple Input Multiple Output (MIMO) system. More particularly, the present invention relates to a transmitting apparatus using an SM method and a receiving apparatus using an SM detection method based on Iterative Maximum Ratio Combining (i-MRC) in a MIMO system.
2. Description of the Related Art
Over the past few years, the wireless communications field has witnessed a remarkable growth, shifting from 3rd Generation (3G) communications to 4th Generation (4G) broadband wireless communications. A radio signal from a transmitter is propagated in multiple paths, not directly to a receiver under a radio communication environment. Accordingly, it is a critical issue to reduce multipath signal distortion.
Compared to a Single Input Single Output (SISO) wireless system, a MIMO system is excellent in terms of capacity and quality. Despite these benefits, the MIMO system has many challenging issues to tackle in order to increase capacity gains. In other words, MIMO transmission is significantly affected by a spatial layout of transmitter antennas and receiver antennas, and synchronization is required among the transmitter antennas. Moreover, there is a shortage of algorithms available for MIMO transmission and Inter-Channel Interference (ISI) occurs at the receiver.
ISI cancellation algorithms have been proposed recently. A major algorithm is a MIMO detection algorithm called Bell Labs Layered Space-Time Architecture (BLAST). A basic BLAST, Vertical-BLAST (V-BLAST), separates multiple transmission data streams and detects them successively by an array processing and interference cancellation technique. A V-BLAST multi-antenna technology utilizes spatial diversity to achieve high Signal-to-Noise Ratio (SNR). While the MIMO system has an improved SNR due to a diversity gain, as spectral efficiency increases, the parallel signal transmission experiences more severe distortion. Accordingly, there exists a need for increasing the spectral efficiency without distortion.
Orthogonal Frequency Division Multiplexing (OFDM) is efficient in reducing the multipath distortion of a frequency selective channel. In OFDM, the frequency selective channel is converted to a set of parallel frequency flat fading channels. OFDM divides a frequency into mutually orthogonal subcarriers to thereby cope with overlapping between signals frequencies. Thus, OFDM utilizes an available bandwidth very efficiently. As a result, OFDM was adopted as the standard for Institute of Electrical and Electronics Engineers (IEEE) 802.11a/16a Wireless Metropolitan Area Network (WMAN) and Wireless Local Area Network (WLAN). However, since a MIMO-OFDM system suffers from high demodulation complexity for each lower-layer subcarrier, an algorithm for reducing the complexity is required.
Accordingly, there is a need for an improved spatial modulation method, and transmitting and receiving apparatuses using spatial modulation for reducing high demodulation complexity.